Acupuncture provides an alternative means of low cost and risk treatment option for pain. Despite the clinical efficacy of acupuncture suggested by a recent NIH consensus panel, the current principles, which govern the practice of acupuncture, are empirical. To facilitate the integration of acupuncture as a viable treatment modality for pain, a neuronal mechanism of acupuncture needs to be established. The long-term goal of the proposed study is to establish a new investigational approach that can correlate and establish the relationship between the analgesic mechanism of acupuncture and the corresponding dynamic brain activities. Based on the preliminary data that we have obtained in the past year, we propose to utilize the following for studying the neuronal mechanism of acupuncture analgesia in human volunteers: 1) a textbook acupuncture paradigm for treating acute pain, 2) a tonic acute thermal pain model, 3) a well established method of modality specific quantitative peripheral thermal neurosensory testing, and 4) functional Magnetic Resonance Imaging (fMRI) of the brain with a data-driven analysis model. This proposed study contains two phases with the following specific aims: 1) To quantitatively establish the effect of acupuncture on pain perception and thermal thresholds by using behavioral measurement and thermal neurosensory testing; 2) To establish the dynamic central nervous system response to the noxious thermal sensory stimulation with individually predetermined noxious thermal heat thresholds by using fMRI; 3) To establish the dynamic central nervous system response to acupuncture by using fMRI; 4) To assess the corresponding effect of acupuncture on peripheral acute thermal heat pain stimulation by using fMRI; 5) To assess the effect of variation in acupuncture needling on pain perception, peripheral thermal thresholds and correlated fMRI indices. [unreadable] [unreadable]